This invention generally relates to toe activated switches for consciously and inconspiciously signaling duress, and more particularly, to a moisture and shock resistant toe switch capable of activating an alarm circuit in a covert manner by movement of the big toe and without causing false alarms.
Prior art toe switches are known for use in activating alarm circuits in a covert manner. One such switch is disclosed in the prior U.S. Pat. No. 3,777,086 of Riedo wherein a switch is built into a shoe or sweat absorbent liner and includes a moving metal part that slides toward another metal part to make electrical contact. The moving metal part is mounted to a flexible membrane material in the region of the balls of the toes and is movable by flexing the toes. The metal parts are not effectively sealed and if wet could give a false alarm. Also, the metal parts are subject to corrosive influences and may not make proper contact when such electrical contact is desired. The constant presence of the movable metal part directly under the balls of the toes can also provide uncomfortable for the wearer and normal flexing of the toes can lead to a higher incidence of false alarms. In addition, in the Riedo device since sliding movement of the metal part must be induced by a force including downward pressure exerted by the toes, sliding movement occurs only after overcoming the substantial forces generated between the liner and the metal plate. Also, the frictional forces induced by toe pressure for activating an alarm circuit can be to some degree dependent upon the amount of wetness in the shoe. This can render the switch inoperative due to excessive slippage between the toe and the membrane, i.e. increase the incidence of false alarms due to uncontrolled slippage between the metal parts. In some instances of high moisture content, the friction between the metal parts of the switch may be insufficient to even counter frictional forces normally occuring during walking.
Other prior art switches use pressure devices or sensors attached to the body to monitor vital signs, such as heartbeat, which signals are sometimes prone to giving false alarms. In some cases, such sensors attached to the body are bothersome and uncomfortable to the wearer.